The proposed research concerns environmental factors that contribute to chronic aberrant behavior in persons with mental retardation. Chronic aberrant behavior such as self- injury, aggression, and property destruction is a major barrier to habilitation and independent living for these person, and it represents a long-standing treatment challenge. Laboratory procedures developed to study basic behavioral processes in animals have shown that prolonged, counterproductive interruptions in behavior (pausing) are generated when relatively rich conditions of positive reinforcement are juxtaposed with lean conditions. Indeed, animals act to escape from these same conditions, even though this action delays or reduces the opportunity for reinforcement, suggesting a functional analogue to aberrant behavior in humans. The proposed research will adapt the procedures from the animal laboratory to study processes potentially operative in escape-maintained aberrant behavior in persons with mental retardation, because functional analysis has established that escape is a primary motive for naturally occurring aberrant behavior in this population. A series of intensive single-subject, steady-state experiments will identify boundary conditions for evoking extended pausing and escape in the performance of standard operant tasks by persons with retardation. The experiments will involve manipulation of reinforcer magnitude, behavioral effort, and discriminative stimuli signaling shifts in reinforcement conditions. The general goal is to develop a laboratory model that can be used for the identification and controlled study of variables that may operate in the natural environment to make otherwise neutral or positive situations aversive.